Renewable fuse end washer



Oct. 13, 1953 F. G. VON HOORN 2,655,577

RENEWABLE FUSE END WASHER Filed Sept. 6, 1951 Fi h /o a /2 u m /0a 6 6 /7 l is) //////A 4 ,9 F

Patented Oct. 13, 1953 UNITED STATES PATENT OFFICE RENEWABLE FUSE END WASHER New York Application September 6, 1951, Serial No. 245,288

Claims.

This invention relates to renewable fuses and, in particular, to an improved end structure for interconnecting integral parts of a renewable fuse.

By renewable fuse is meant generally that type of electric safety valve wherein a replaceable fuse link is connected across a of knife blades in such a manner that the link will melt and open the circuit between the knife blades when a predetermined current passes through the link. Renewable electric fuses have long been known in the art, as shown, for example, by United States Letters Patent 2,471,176 von Hoorn, assigned to the same assignee as the present invention.

With renewable fuses, however, gr at care must be taken in removably securing the fuse link to the knife blades. If a positioning means is selected which does not insure a substantially rigid alignment of components, the resulting relative movement causes deformation of the fuse link, loosening of contacts, or combinations of these that alter the characteristics of the fuse link and cause malfunctioning of the fuse.

In conventional renewable fuses, one of the parts is an insulating spacer which positions a pair of knife blades for contact with a fuse link. The interconnection of the spacer bar with the knife blades must be such that there can be no rotation of the blade relative to the bar; otherwise, the assembly might loosen to create a high resistance at the point of contact or the link might be bent or deformed so as to malfunction.

A considerable amount of thought has been expended perfecting the conneetion between the insulating bar and the knife blades, but there is still need in the art for an improved interconnection between these parts.

Accordingly, it is an object of invention to provide an improved assembly for interconnecting a knife blade, an end washer and an insulating bar.

It is a further object of my invention to provide an improved end washer having spaced lips on its inner face to provide for alignment of an insulating bar.

It is a still further object of my invention to provide an improved end washer having raised lips on its inner face, so constructed that the lips are adapted to accommodate different sizes of insulating bars.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly, this invention relates to an improved renewable fuse structure having a pair of end Washers, each cast from a sintered metal to have a pair of raised lips on their inner faces thereby to provide for the secure engagement between an insulating bar and spaced apart knife blades.

In the drawing, Fig. 1 is a front View, partly in section, of my improved fuse structure; Fig. 2 is an exploded view showing the inter-relationship of a knife blade, washer, and insulating bar; Fig. 3 is an end elevation of one surface of the improved end washer; Fig. 4 is a side view, partly in section of the end washer shown in Fig. 3 and taken along the plane a-a thereof; while Figure 5 is a bottom plan view of the fuse link structure or assembly of Figure 1.

In the drawing, a renewable fuse I is shown comprising a pair of knife blades 2 and 3 and a casing i.

Casing or housing 4 encloses a fuse link 5 and an insulating bar 6, both of which are secured to the inner edges of the spaced knife blades 2, 3.

Knife blades 2 and 3 are made of one of the better conducting materials, such as copper, coated generally with a light silver plating to prevent oxidation of the copper. The knife blade has such a shape that it provides a wide spring clip engaging portion '1', a shoulder S and an inner or link engaging portion 9. Shoulder 8 is constructed as a stop to prevent the axial insertion of the knife blade into housing 5 beyond a predetermined limit, while the clip engaging portion I is constructed to facilitate the insertion of the fuse into an electric circuit having spring clip or other types of terminal.

Housing 4 comprises a cylinder or cartridge ia made of any one of the insulating fiber compounds, such as vulcanized fiber, and a pair of end closures i9 and I I. Closure I0 is held in engagement with cylinder do by some means, such as by the inter-engagement of the threads 12 on the cartridge and the threads I3 011 the closure. When the closure H1 is threaded into cartridge 4a, either the threads are upset or a pin or rivet I4 is passed through both the housing and the closure [0 to prevent the closure from being unscrewed. Closure iO further has a radially inwardly extending lip [0a which acts as a stop. Lip lea is either slotted or of such a size that clip portion 1 can pass through it.

At the opposite end of the fuse, however, a ferrule I5 is inserted into the cartridge 4 in such a manner that a portion of it extends axially screwed from nipple it to allow for the insertion,

or removal of the fuse link structure or assembly [8, as will be hereinafter described, Ffuse link.

structure I8 comprises insulating bar B and fuse link 5, with a blade 2 and a washer l9 positioned at either end. The structure-issuchthatwasher I9 is placed over the narrow portion 9 of knife blade 2 until it strikes shoulder 8, whereupon insulating bar 6 is superimposed on the narrow portion 9 of blade 2 to be secured thereby some means, such as by screwsor bolts 20. To facilitate this assembly, the narrow portion S is; provided with a bore 2i while'the insulating bar has a registering bore22.

The arrangement of the fuse link assembly is such that insulating bar 5 butts up against the inner surface of washer l9 and holds the lat er against shoulder 8. of knife blade 2. When this has been done at both ends of the insulating bar 5, a fuse link 5 is positioned on the knife blades 2, 3 to be held in place by bolts 28.

When the fuse link structure is thus constructed, it is a rigid assembly which can be integrally removed from or inserted into the fuse cartridge l. When in the housing, lips Mia and ll of the closures H II respectively butt up against the outer surfaces of washers [9 to position the fuse link structure [8 axially relative to the housing.

Washer I9 is cast from a sintered composition to provide a pair of upstanding lips or shoulders 23, 24 which are positioned adjacent a slot 25 out centrally in the washer to permit it to slide over the narrow portion 9 of knife blades 2, 3. Shoulders 23, 2 are spaced apart a distance equal to the width of insulating bar 6 to permit insulating bar E5 to be butted up against the inner face 26 of washer l9 between the lips 23, 24. Then when knife blade 2 is passed through slot 25 and the securing means 20 is used to lock bar 6 to the inner end 9 of insulating bar 2, a rigid structure is provided to prevent any twisting of the knife blade relative to insulating bar 6 or to the axis of bolt 20.

By making washer H! of a sintered metal, no expensive machining operations are required in the process. Machining operations would raise the price of the washer, thereby limiting its use in fuse structures. The sintered washer is compatible with mass production techniques and has been found to meet the rigid requirements of the Underwriters Laboratories, Inc.

A further embodiment of; this invention is shown in Fig. 3 wherein the raised lip or shoulder portions 21, 28, which are positioned on the inner face 26 of washer [9, are L-shaped. This specific contour is given to the shoulders 21, 28 to provide for the securement of either of two sizes of insulating bar 6; that is, a narrow bar can be positioned between the facing base portions of the L, 29, 39, while a wider bar can be positioned between the facing stems of the L, 3l, 32.

In building fuses it is important that the proper sizeinsulating barbe used with a fuse link; that is, experience in the art specifies the minimum bar size for a certain fuse rating. Accordingly, to reduce manufacturing costs, manufacturers would like to save as much material as possible; that is, they would like to use a small insulating bar where possible and use a larger bar only where the fuse rating demands it.

With my novel structure shown in Fig. 3, one fuse washer, which is adapted to mass production techniques, is compatible with two sizes of insulating bars. With this arrangement for the fusenvasher, a manufacturer can stock fewer parts.

InFige, the dimensions of the shoulders 21 are shown relativeto the thickness of the washer, and it is understood that there is no particular limitation on the dimensions of these raised portions except that they should be maintained as smallaspossible to provide for the use of a minimum amount of material. In the example shown, the lips are raised about one-fifth the thickness of the washer.

Modifications of this invention will occur to those skilled in the art and it is desired to be understood, therefore, that this invention is not intended to be limited to the particular embodiments disclosed but rather it is intended to cover all modifications which are within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

i. In renewable fuse having a pair of knife blades, each blade having a narrow inner end a wide outer end, said blades being detachably connected together by both an insulating spacer bar and a fuse link, said bar and link being contained within an insulating housing, the invention comprising end washers for sealing the space between the knife blades and said housing, said washers having a central slot to receive the narrow inner portion of the blades so that the washers are disposed between the wide outer portion of the blades and the ends of the spacer bar, the inner face of each washer being provided with projecting means which engage with the side edges of said bar to prevent any misalignmen-t between the blade and the spacer bar.

2. In a renewable fuse having a pair of knife blades, each blade having a narrow inner end and a wide outer end, said blade being detach" ably connected together by both an insulating spacer bar and a fuse link, said bar and link being contained within an insulating housing, the invention comprising an end washer for sealing the space between the knife blades and said housing, said washer having a central slot to receive the narrow inner portion of the knife blade so that the washer is disposed between the wide outer end of the knife blade and an end of the spacer bar, the inner face of each washer having mounted thereon a pair of lips to prevent any misalignment between the blades and the spacer bar.

3. In a renewablefuse as recited in claim 2 wherein thesaid lips engage the side edges of said bar.

4. In a renewable fuse comprising a pair of knife blades, an insulating bar, a fuse link and an insulating housing, an end washer for sealing the end space between said knife blades and said housing said end washer comprising a disc slotted centrallyv to receive a portion of said knife blade which extends into said housing, and a pair of integral projections mounted on the inner face ofsaid washer to engagethe side edges of said bar so as to prevent any misalignment between the blades and the spacer bar.

5. In a renewable fuse having a pair of knife blades, each blade having a narrow inner end. and a wide outer end, said blades being detachably connected together by both an insulating spacer bar and a fuse link, said bar and link being contained within an insulating housing, the invention comprising end washers for sealing the space between the knife blades and said housing, said washers having a central slot to receive the narrow inner portion of the blades so that the washers are disposed between the wide outer portion of the blades and the ends of the spacer bar, the inner face of each washer being provided References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,656,121 La Mar Jan. 10, 1928 2,079,097 Wood May 4, 1937 2,560,138 Swain July 10, 1951 

